STRUCTURAL PHENOMENA RELATED TO ASSOCIATIVE AND DISSOCIATIVE ADSORPTION OF WATER ON NI(110)

The adsorption of water on Ni (110) has been studied by thermal desorption spectroscopy (TDS), work function (DELTA-PHI), Fourier transform infrared reflection-absorption spectroscopy (FTIR-RAS), low energy electron diffraction (LEED), and electron-stimulated desorption ion angular distribution (ESDIAD). The major findings of this study are the following: (1) Water molecules in the chemisorbed c(2 X 2) half-monolayer do not cluster and the plane of the molecules is highly inclined to the surface normal; (2) no ESDIAD evidence of oriented water dimers is observed at 130 K and no FTIR activity is observed following adsorption at 80 K until multilayers are populated; (3) water has been measured to partially dissociate at a minimum temperature of 205 +/- 2 K; (4) the binding energy of water to the Ni (110) surface is increased by H-bonding to adsorbed hydroxyls (produced by the partial dissociation) in a linear OH(ad)/H2O complex with planar symmetry in the [001] direction. This bonding results in a higher temperature desorption state (A1).